I have been trying to figure out what type of system meets my needs and the documentation is incomplete.

http://developer.authorize.net/api/compare/

That chart doesnt mention multiple items, stores, checkout, posting methods, etc.

I dont have SSL so I need it off site. I need to be able to add multiple items for one transaction. I want to go from click to buy right to credit page, but also need the ability to return to add more if desired. In effect I need the post page to send the item info directly to the script so there in no intermediate page.

Thanks in advance for your help.